Grad Student Research on Past Climate Change Could Help Today’s Whitebark Pine Trees

Maegen Rochner with a whitebark pine remnant log in the Beartooth Mountains.

A UT graduate student’s climate change research could aid researchers and conservationists working to save a threatened tree species known as whitebark pine—and by extension, preserve the primary food source of an American icon, the grizzly bear.

Maegen Rochner, a second-year doctoral student in the Department of Geography, is using tree rings in both living and dead whitebark pine trees to investigate the impact of climate change on a high-elevation ecosystem in the Beartooth Mountains of Wyoming. The results could provide more knowledge about what the future might hold for a threatened species.

Whitebark pines are a threatened species in the northwestern United States and endangered in Canada. Their destruction would affect grizzly bears and other animals that depend on the seeds of whitebark pine cones for food, and cause major alterations to fragile ecosystems throughout the western United States.

Rochner first became interested in whitebark pine research in 2014 as a graduate research fellow for the National Science Foundation–funded North American Dendroecological Fieldweek in Cody, Wyoming. She was part of a group that studied the influence of climate on a changing treeline in the Beartooth Mountains. Henri Grissino-Mayer, UT professor of geography and a tree-ring expert, was a group leader at the same field week and is now her advisor.

Rochner and Grissino-Mayer noticed that giant logs litter the landscape near the range’s treeline (at an elevation of 10,000 feet) and decided to investigate. Today, there are no trees similar in size to these logs, only younger whitebark pine and Engelmann spruce trees that likely began growing in the past 300 years. The logs, however, had been trees that likely grew to be well over 500 to 1,000 years old.

Rochner and Grissino-Mayer hypothesized that these dead whitebark pine trees lived through the Medieval Warm Period (the years 1000–1300) but were nearly wiped out during the Little Ice Age (1400–1800). To investigate, they collected samples from the logs and are working to determine their age, using techniques similar to those used for historic structures. So far, the oldest of these samples is a whitebark pine tree that began growing in the year 792.

Rochner also collected core samples from living whitebark pine trees and is investigating how they have responded, and are currently responding, to climate. So far, results indicate that the trees prefer a warmer spring and fall and less winter snow, or an extended growing season. However, warmer temperatures have also increased attacks from the native mountain pine beetle and a human-introduced invasive fungus, both of which thrive in warmer conditions.

“Because temperatures are getting warmer, tree populations that used to be protected are now being attacked,” Rochner said. “And in other areas where the return of cold winter temperatures once moderated mountain pine beetle infestation, the pest is now killing trees at unprecedented rates.”

As a next step, Rochner wants to interview rangers of the US Forest Service and National Park Service to discuss how whitebark pine research, including her own, can be more useful in conservation and management efforts. She hopes to better understand how researchers can help with tough decisions about possible long-term solutions, such as assisted migration or planting whitebark pine in colder high-elevation and high-latitude environments.

“If the climate keeps getting warmer, assisted migration might only be a short-term benefit,” she said.

Rochner presented her research this past weekend during the annual meeting of the American Association of Geographers in Boston. She has received several top awards to continue her groundbreaking research, including one from the Whitebark Pine Ecosystem Foundation, a Montana-based organization dedicated to counteracting the decline of the whitebark pine population.

CONTACT:

Lola Alapo (865-974-3993, lalapo@utk.edu)